CHOPP3R is a search-and-rescue helicopter made from a single 31313 Lego Mindstorms EV3 set. I built this as a potential model for a book, but as the book has not materialised I decided to publish it instead! CHOPP3R has working top and rear rotors driven my a medium motor. It searches for a liferaft containing the beacon using the IR sensor mounted under the cockpit. There is a winch mounted on the side to lower a rescue rope that is controlled using the up/down buttons on the EV3. I’m particularly pleased with this model as it looks realistic and yet only uses a single 31313 EV3 set to build. It just shows you that a single set can give you a lot of flexibility.

The Chopp3r.ev3 control program for CHOPP3R is broken into four parts.

1. Monitor the touch sensor. If it is pressed then toggle the boolean variable flying
2. If flying is true then turn on the rotor motor, otherwise turn it off.
3. If flying is true then get the distance reading from the IR sensor and use that to compute the delay between beeps.
4. Monitor the up/down buttons and power the winch motor.

To use this model all you need to do is:

1. Press the top button on the IR beacon to put it into beacon mode; the green LED in the IR beacon should illuminate.
2. Download and run the program on the EV3.
3. Press the touch sensor to start the rotors.
4. As the chopper gets closer to the IR beacon the beeps will get progressively quicker.

I made building instructions for this model available as a RescueChopper.pdf. Be warned; it’s a 21MB file so best to right-click and Save As… before viewing.

ERRATA: There is a mistake in the building instruction PDF at step 25. Two parts are missing to hold the EV3 onto the Chopper body. You need to attach a Technic Beam 3 x 3.8 x 7 Liftarm Bent 45 Double (part 32009) to both sides of the EV3. See the pictures in the gallery below for details.

CABLES: Connect the cables as follows:

• Motor A: small motor driving the rotors
• Motor D: winch motor
• Port 1: Ultrasonic sensor
• Port 4: Touch sensor